As is well known in the art, the typical systems and methods for processing oil sands are relatively complex, and require significant water and energy inputs. In particular, the typical processes involve the use and contamination of large volumes of water and the creation of large waste (tailings) ponds. Large volumes of CO2 emissions (and emissions of other gases, e.g., NOx, SOx, and H2S) are generated by heating the large volumes of water by combustion of fossil fuels, to the extent that oil sands processing has become a major contributor of CO2 emissions. Because the conventional systems and methods typically involve transporting oil sands, and waste sand resulting from the processing thereof, over relatively large distances, significant maintenance costs are also incurred due to the abrasion to which equipment is subjected.
A typical process of the prior art is schematically illustrated in FIG. 1. (As will be described, the balance of the drawings illustrate the present invention.) At the step identified as 21, oil sands are excavated. In step 22, the excavated oil sand is transported to the ore preparation plant 24, where the ore (i.e., excavated oil sand) is screened and crushed as required. As is well known in the art, various means may be used for the excavation of the oil sands and its transportation to the ore preparation plant 24.
In connection with conventional processing, hot water (typically heated by natural gas) is also added, at step 26. As is well known in the art, a large amount of water is used in this step. In step 28, a portion of the sand is separated from crude bitumen (i.e., liquid or semi-solid raw petroleum) in the oil sand. More hot water is added at the initial separation of sand and bitumen, at step 30. Following sedimentation (step 32), the waste is sent to a waste pond (step 34). The bitumen, and the portion of the sand remaining with the bitumen at this point, is then cleaned (step 36). In this step, the sand typically is cleaned with naphtha, to remove any bitumen remaining with the sand at this point. The sand removed in this step is also sent to sedimentation (step 38), and subsequently to the waste pond (step 40).
The bitumen remaining is then upgraded (step 42), and the bitumen is subsequently mixed with diluents to form “dilbit” (step 44). The diluents are less viscous than the bitumen, so that the viscosity of the dilbit is such that the dilbit can be pumped. The dilbit mixture of diluents and bitumen is then transported to a refinery (step 46), at which the bitumen and the diluents are separated, and the bitumen is refined to produce high-value products. Such high-value products include, for example, gasoline, diesel fuel, naphtha, and petrochemical feedstock.
The many disadvantages of the conventional processing described above are well known in the art. For instance, the conventional processes consume up to five barrels of water for every barrel of extracted bitumen. The waste ponds (also referred to as tailings ponds) required in connection with conventional processing cover large areas and emit toxic compounds such as volatile organic compounds and toxic effluents to the surrounding environment (e.g., into the Athabasca River). The widespread modified landscapes resulting from mining are also sources of harmful substances, and substantial costs are incurred in connection with reclamation efforts.
In addition, the diluents used in the dilbit (i.e., to reduce viscosity) are high-value products that could be profitably used elsewhere.
As is well known in the art, the dilbit typically is transported thousands of kilometers via pipeline or railroads. This necessity creates significant risks, the most important of which is the risk of environmental damage due to a break or leak. Because of the nature of the components of dilbit, a spill of dilbit into the environment typically has serious consequences. When dilbit is released in an uncontrolled manner, the dilbit is initially relatively less viscous (i.e., due to its diluents content), and readily drains into the ground or water near the pipeline. However, shortly after the dilbit's release and drainage into the ground, the diluents tend to escape into the atmosphere, ultimately resulting in a more viscous residue (consisting primarily of the bitumen in the dilbit) distributed in the soil or water. As a practical matter, remediation of the viscous residue is difficult.
The activities in a group identified as “A” in FIG. 1 typically may take place within distances in the order of about 10 kilometers. The activities in the group identified in FIG. 1 as group “B” conventionally are carried out at greater distances, e.g., such activities may be carried out at distances that are on the order of hundreds of kilometers apart. Also, the activities in group “C” usually are carried out at distances on the order of thousands of kilometers apart. Accordingly, to transport the materials in question requires additional energy consumption, adding to processing costs and also resulting in further CO2 emissions.